1. Field of the Invention
The present invention relates to an image display apparatus using an electron-emitting device.
2. Related Background Art
A planar display which arranges many electron-emitting devices as electron sources on a planar substrate, irradiates phosphors of image forming members on a substrate with electron beams emitted from the electron sources on the opposite side to make the phosphors emit light and display images, requires the inside of a vacuum chamber accommodating the electron sources and the image forming members to be kept in a high vacuum. This is because an increase of a pressure due to generated gases in the vacuum chamber, though the extent of the effect depends on the types of the gases, adversely affects the electron sources to decrease an electron emission amount and hinder the display of a bright image.
Gases generated from image display members accumulate in the vicinity of an electron source before reaching a getter installed outside an image display area, locally increase pressure and deteriorate the electron source, which is a peculiar problem particularly to a planar display. Japanese Patent Application Laid-Open No. H09-82245 describes a method of arranging the getter in an image display region and making it immediately adsorb the generated gases to inhibit the deterioration and damage of elements. In addition, Japanese Patent Application Laid-Open No. 2000-133136 shows a configuration in which a non-evaporable getter is arranged in the image display region, and a evaporable type getter is arranged outside the image-display region. Furthermore, Japanese Patent Application Laid-Open No. 2000-315458 shows a method of performing a series of operations including degassing, getter forming and seal bonding (making the chamber into a vacuum) in an evacuating chamber.
There are a evaporable type getter and a non-evaporable getter in getters. The evaporable type getter has an extremely high speed of eliminating water and oxygen, but has a speed close to zero of eliminating an inert gas such as argon (Ar) (as does the non-evaporable getter). Argon gas is ionized by an electron beam to become positive ions, which are accelerated in the electric field that is provided for accelerating electrons and bombard the electron sources, damaging the latter. The positive ions further may discharge inside the vacuum chamber and damage the apparatus.
As for exhausting means capable of exhausting an inert gas, Japanese Patent Application Laid-Open No. H05-121012 describes a method of connecting a sputtering ion pump to a vacuum chamber of a planar display and keeping the vacuum chamber into a high vacuum for a long time.
The planar display, as shown in FIG. 9, has a configuration of a vacuum chamber 906 in which a face plate 109 having a phosphor film 901 and a main body 905 of a vessel are hermetically sealed with a sealant 902. An electrode body structure 904 is arranged in the above described main body 905 of the vessel, has a field emission type cathode, modulates electron beams emitted from the cathode with an internal electrode 903, in other words, a modulating electrode, and direct them toward the phosphor film 901 to display images. An ion pump 908 is connected to the main body 905 of the vessel for the purpose of keeping a vacuum. The ion pump 908, for instance in one embodiment, applies 1,000 gauss (0.1 tesla, the unit tesla of magnetic flux density is hereafter shown as T) by a magnet 121.
However, in a configuration in which an ion pump 908 is connected to a vacuum chamber 906 through a metallic seal 907 such as an ICF flange, a heavy metallic seal made of a metallic material is maldistributed in one side of a planar display. In addition, a magnet is directly attached to the ion pump chamber 120 without a yoke (ferromagnet), so that the ion pump chamber also becomes heavy. For this reason, the configuration causes problems of deforming or damaging a part for attaching the metallic seal 907 to the main body 905 of the vessel, when the ion pump 908 and the metallic seal 907 are joined to a main body 905 of the vessel, causing a leak of a vacuum in the vacuum chamber 906, and lowering a manufacturing yield.
In addition, the configuration has also a problem that noises caused by discharge having occurred in an ion pump interfere with an image in an image display apparatus.